Skip to content

Leave a layer out sometimes

Give a layer an absent chance: the share of assets that skip it entirely. A hat that only one asset in ten wears, a glow that usually is not there, a trim that makes a character a chase item.

Why not just add an empty variant

A transparent variant looks the same, but it costs you. On a Dynamic layer it still rolls a color, so two assets that both show nothing can have different DNA, and the unique DNA figure inflates for no visible reason. An absent layer rolls no color and contributes nothing to the DNA: two assets that both leave it out agree about it.

The chance lives on the Recipe, not on the layer, because one layer (.igt) can sit in several Recipes. The same hat can be common on one character and rare on another.

In the app

  1. Unlock editing (click the read-only chip in the title bar).
  2. Select a Recipe in the tree.
  3. In the LAYERS header, click OPTIONAL LAYERS. An ABSENT column appears.
  4. Type a percent into the layer's row and leave the field (Tab or Enter). 0 means the layer always appears. 100 means it never does: the layer is shelved, not deleted, the same meaning a Recipe weight of 0 carries.

Turning OPTIONAL LAYERS off asks first, then clears every chance in the Recipe.

On the layer's own panel, an absent 72% flag appears. The shares in its variant table already account for it, so they are the odds of getting each variant, not the share among its siblings: a variant that is 1 in 20 of the times the layer shows, on a layer shown a tenth of the time, reads as well under 1%.

From the command line

nfty set chance cat.rcp --id hat --absent 90
nfty set chance cat.rcp --id hat --absent 0      # always present again
nfty stats book.cbk                              # prints each chance, and what it does to the odds

--id is the layer's id, not its display name; nfty inspect cat.rcp lists them.

What it does to the numbers

  • The seed still reproduces. The absent outcome is drawn ahead of the layer's variants and never mixed into their weights. A book that uses no absent chance rolls byte-identically to how it did before the feature existed.
  • Unique DNA changes. An optional layer adds one shape (absent) beside its present shapes, so the count is a sum rather than a plain product. The CookBook panel and nfty stats show the new figure.
  • Rules still apply. A rule fires only when its trigger layer is present with the named variant. An absent layer cannot trigger a rule, and an Exclude target that is absent is never a violation. A Require target that is absent is: the roll is rejected and rerolled.

See also